I first met Rufus Sewell a decade ago, when he was playing Macbeth in Bath, full of vigour and hope for the part, but still incurably larky. He seemed like the naughtiest boy in school, blessed with an easy intimacy, a filthy chuckle, a subversive streak, but with more charm than insolence, and on the way to acclaim via many parties and good-looking girls, including what he then described as “a bit of a snog” with Kate Winslet, now a huge mate.

Ten years, two marriages and a seven-year-old son later, the trademark raven tousles remain, but it is a different actor, now 41, I find sipping Diet Coke on a sofa in Soho House. His beard is streaked with grey (“Better than the ginger sprouts I used to have...”), but the wide green cat’s eyes are clearer than before, and the zealously sparkling teeth attest not just to starring in a CBS drama, 'Eleventh Hour', for which he moved to LA, but a whole new regime. He is bronzed and relaxed in his jeans and layers of knitwear. “Didn’t know what the photographer would want, darling,” he jokes. He no longer smokes or drinks; he doesn't want to “crap on about it”, but the late nights had been running him down. “I’d had a good laugh and I’d had a good drink. And now I don’t.”

He says the best thing about living in the Hollywood Hills community of Beachwood Canyon was the 14-hour days, which left no time for partying. We laugh about his old haunt, the Groucho Club. When I tell him I left when I realised I only ever visited it to use the loo, the old reprobate returns for a second: “But that’s where all the action happened anyway.”

That was then. He has been through two short marriages — one to a fashion consultant called Yasmin (who kept the name), and another to the writer-producer Amy Gardner, from whom he is separated, mother of his son, Billy — not to mention a long relationship with Helen McCrory, who seemed to match him like a twin: a pair of lustrous, dark-haired, deeply serious jokers. And now he is, what? Sober, thoughtful, slightly — but not fatally — disenchanted by the business that once promised so much, but failed to deliver on the interesting, complex leading-man roles.

He used to rail against being misunderstood and underused, announcing, a couple of years ago, that he never wanted to play another villain. He’s wiser these days, no longer wishing to appear grumpy or ungrateful. Instead, he has taken a dramatic, not to mention admirable, route by accepting only work that interests him and is substantially different from the role that preceded it.

It is a recipe for long-term unemployment, but one he describes as “ the only power I have”, and one he will see through to the penurious end if needs be. “The main artistic choice I make is about how simply I can live. I’m not tempted to have the big house with the swimming pool, because then you have to support that lifestyle.”

Sewell has flown in for a few days from Hungary, where he is filming 'Pillars of the Earth', based on a Ken Follett novel, in which he plays a 12th-century stonemason whose life’s work is to build a cathedral. “He works outside, so I’m allowed to go on holiday to get a tan,” he laughs, seeming happy with the job. “It’s lovely to play a good man, rather than someone you wouldn’t let near your children. I got so tired of reading scripts that wanted the cruel twist of the mouth.” They have also required, at various stages, the depressive artist, like Mark Gertler in ''Carrington', the comedy yokel Seth Starkadder in 'Cold Comfort Farm' and the lovelorn idealist in 'Middlemarch'; but Sewell remains resolutely focused on striving for better.

He concentrates on small films these days. His latest, Fabrice Du Welz’s 'Vinyan', the story of two increasingly demented parents searching for a child lost in the tsunami, was made for less than $5m. “For me, the lower the budget the better, because there’s more chance of me getting an interesting part.” The problem is that bargain-basement pictures, with their big-fish/small-pond opportunities, might not necessarily be well regarded enough to be helpful in his quest. He made 'Vinyan', which represented the kind of part he was frustrated about not being offered, back to back with the equally dark 'Downloading Nancy', about a woman with a sadomasochistic internet life who finds someone to murder her — “Bundle of laughs, that one.” Did the line of work depress him? He laughs. “No, they cancel each other out.”

With 'Vinyan' shot in the Thai jungle, his character is eternally grief-stricken, paranoid, assailed by mosquitoes, monsoons and an ever more unhinged wife, played with alarming veracity by Emmanuelle Béart. How uncomfortable was it? “The less than thrilling discovery on your way into the jungle,” he laughs, “is that your director’s hero is Herzog.” Yet he and Béart, who might have been spoilt and superior, but wasn’t, traded jokes over polystyrene cups of tea as the wildlife crept and crawled around them. “I had this nightmare vision of a humourless French actress...” He slips into a pouty mademoiselle accent rather too well. “‘Ooh, we like to play zee clown? Not everyfing is funny, Meester.’ But Emmanuelle passed my own personal sense-of-humour test — she laughs at my jokes...”

By the end of the shoot, however, as the fictional couple dissolved, the star was mostly nestled in his trailer or his beach-hut hotel, improving his mind, to make up for losing it in the story. “After I’d exhausted Brickbreaker on my BlackBerry, it was time to read the classics.” With a typical swerve off course, he read not Heart of Darkness or Lord of the Flies, but the first volume of A la recherche du temps perdu. “And Robert Mitchum’s autobiography, which I think was a great companion piece for Proust.”

Get him on the wrong subject and Sewell can be defensive; verge too closely on the personal and he beats you back (and, frankly, after two mini-marriages, who wouldn’t be wary?). Make any easy assumptions and he tells you how wrong you are. He used to confide about being a fat kid, but now says that was only because an interviewer asked him what it was like to be a swarthy, Byronic (junior) love god. What annoys him even more is the snooty assumption that his first love is theatre, which has taken root after so much acclaim for his stage work. “I always wanted to be a film actor,” he says. “I still do.”

For Jan, in 'Rock’n’Roll', Tom Stoppard’s play about emerging democracy in Czechoslovakia, he won best actor in the 2006 Evening Standard Awards; and he launched his career playing the tutor Septimus Hodge in the original 1993 production of Stoppard’s 'Arcadia', with Felicity Kendal and Bill Nighy, directed by Trevor Nunn at the National Theatre, a part he accepted grudgingly, because it wasn’t a movie. He laughs at that callow ingratitude: “By the time I was offered 'Rock’n’Roll', I knew how lucky I was. But the point is, if 'Rock’n’Roll' had been a film, I’d never have been offered that part.” Because his profile isn’t sufficiently bankable?

Right now, Sewell is the rootless traveller — “weightless”, as he puts it — floating between his film location, a friend’s spare room in London and LA, where the lease on his house expires in December. “I don’t know where I’ll be living, which I find exciting,” he says. “I don’t have anywhere. I don’t have stuff now, and I’m happy without it. I feel very free.” Moreover, his son, Billy, loves flying back and forth to see his father. “My mum brings him over and we have adventures together.”

Sewell’s mother, Jo, who once sold vegetables from the back of a van to feed her two sons, is his heroine; he can’t have been an easy teenager to raise, with his attention-seeking and truanting. “In fact, she credits her experience with me for making her become a social worker.” At London’s Central School of Speech and Drama, he messed around, skipped classes, was threatened with expulsion, before Judi Dench saved him, directing him as the Porter in 'Macbeth' and helping to find him an agent. “Naughtiness is glamorising it,” he says baldly. “I was just useless, naturally lazy and not very together. I’d be late and not have a good enough excuse, so I’d hide. I was pathetic. Just a bit rubbish. I was afraid of rehearsals, because I was worried that I could only act by accident, and if I applied a work ethic, I’d disintegrate.”

Partly, though, the irresponsibility was a personal tribute to his Australian animator father, who died when Sewell was 10, by all accounts a charmingly unreliable character. “Always turning up late, but with presents, and getting away with it. I thought that was cool. It took me a while to get over it.” He smiles: “Now I’m on time.” He found the job security in making the potentially long-running 'Eleventh Hour', in which he played a brilliant crime-solving biophysicist, oppressive. When it was cancelled earlier this year, he felt only relief. “I quickly felt more trapped than anything. I was uneasy. I would rather have the insecurity, and if that means unemployment nine months a year, then I’ll go with that.” He wants more than anything to be a “useful” actor, as Anthony Hopkins, John Hurt, Ian Holm once were, able to play the butler or the lord with equal and easy perfection.

When I ask how much of his work has really felt as if it mattered deeply over an 18-year career, he shrugs a little sadly: “Two or three pieces: 'Rock’n’Roll', 'Charles II', ' The Taming of the Shrew ' [a 2005 modern-day TV version, which he likes for its opportunity to do comedy].” “As I get older,” he muses, “I think people are more inclined to believe that I am a character actor.” And if they don’t? “I’d rather be me now than when I was in my twenties, anyway. I just didn’t believe in myself as an attractive person at all.” Smouldering, sooty-lashed, chiselled Rufus? Can that be true? “Oh, yes, absolutely.”